Project Summary/Abstract N6-methyl-adenosine (m6A) is the most abundant internal modifications in messenger and long non-coding RNA. This modification occurs in many sites in mRNA with functions including splicing, export, localization, stability, translation, and immune response. Functional inquiries of the m6A modification have been intensely studied since 2011 and have become an integral component of the new field of epitranscriptomics. Studies from our laboratories and others indicate that m6A modifications exert their function through interactions with specific cellular proteins termed m6A readers. This proposal investigates the biological function of m6A reader proteins and addresses the underlying molecular and cellular mechanisms. Our proposed research will establish molecular models of m6A function in cells through two nuclear-localized m6A reader proteins and their mechanisms of action. Aim 1 will investigate the molecular and cellular mechanisms of co-transcriptional, m6A-dependent regulation of mRNA alternative splicing. We will test our model on HNRNPG/m6A-dependent control through RNA polymerase II pausing and the effect of nascent RNA structure using targeted approaches. Aim 2 will study the function and mechanism of HNRNPG assembly through a low-complexity region and the effect of assembly on interacting with m6A-modified RNA and alternative splicing. We will test a molecular model on these aspects using biochemical and cellular approaches. Aim 3 will study the m6A-dependent mechanism of two nuclear-localized m6A reader proteins that regulate transcriptome-wide alternative splicing. We will elucidate the interplay among these two proteins on specific exon targets and how this occurs.